Mango, that really is some detailed craftsmanship you've put into that car. I like that you took the time to clean, polish and paint all of the bits before you installed them. And you're a pretty darned good hand at fabbing up little bits for those that didn't quite work the way you intended them to -- little bits of that are all over in those detail photos.
Mostly, I like how it all came together so cleanly. I'd have probably lost my damned mind.
Jack/Jake, how is the car set for space under the doors, in the longitudinal channels? In my car, the channels on both sides are wide open. If you were to fab up an aluminum box to keep the elements out, you might have enough room. You did say the unit wasn't very big, right? Plus, running the intake and exhaust would be cake.
Second thought on the same issue; how about space inside the tunnel, maybe? Is there enough clearance in there for a heater, if you made an access panel like Lane's (and everybody else's) Beck has?
I don't know how big the heater unit is, but it seems to be a single-event setup, with no maintenance except an annual check, right? I'd think it would be possible. Maybe ahead of the pedals, behind the frame head?